Have a sneaking suspicion that your guy might be cheating on you? Check his waistline.

According to a new study, men lose an average of six pounds when they're sneaking around. (Um...can we say busted?)

Why does weight drop away along with fidelity? For one, sneaking around on your number one is stressful, and researchers say that stress is a known pounds shedder.

Then, there's the fact that wayward dudes are likely to adopt a fitness routine so their bods look hot for the new ladyfriend. (It should be noted that the same weight-loss effect was found in cheating women—though, we lose an average of 10 pounds when we're having an affair.)

So should we hope our men are lazy asses who park themselves on the couch for all eternity? We think not. But if you notice your notoriously, lovably schlumpy guy starting to pump iron on the reg, either he's trying to get fit and be hotter for you—or perhaps you have reason to suspect something's up.